From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 30830 invoked by alias); 24 Dec 2002 18:08:52 -0000 Mailing-List: contact cgen-help@sources.redhat.com; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cgen-owner@sources.redhat.com Received: (qmail 30789 invoked from network); 24 Dec 2002 18:08:50 -0000 Received: from unknown (HELO seba.sebabeach.org) (64.165.110.50) by 209.249.29.67 with SMTP; 24 Dec 2002 18:08:50 -0000 Received: by seba.sebabeach.org (Postfix, from userid 42) id 8BB6AB539; Tue, 24 Dec 2002 10:14:58 -0800 (PST) From: Doug Evans To: dj@redhat.com Cc: geoffk@geoffk.com, cgen@sources.redhat.com In-reply-to: <200212241752.gBOHqxJ28997@greed.delorie.com> (message from DJ Delorie on Tue, 24 Dec 2002 12:52:59 -0500) Subject: Re: opcode bits beyond base-insn-bitsize References: <20021224055735.2F216B539@seba.sebabeach.org> <200212241752.gBOHqxJ28997@greed.delorie.com> Message-Id: <20021224181458.8BB6AB539@seba.sebabeach.org> Date: Tue, 24 Dec 2002 10:08:00 -0000 X-SW-Source: 2002-q4/txt/msg00126.txt.bz2 Date: Tue, 24 Dec 2002 12:52:59 -0500 From: DJ Delorie > Can anyone remember what the details are? > i.e. what didn't work? assembler? disassembler? simulator? xstormy16 has both 16bit and 32bit opcodes, and some of the 32bit opcodes have decodable bits in the second half. The base-insn-bitsize is used to set up the masks and such, so it needs to be at least as big as the largest decodable bits. s/needs/needed/ There is no intent that this is how things should work. IIRC the simulator fetches and decodes additional bits as necessary. In the case of opcodes support, there should be additional masks as appropriate. The tricky bit is when the 32-bit opcodes are mixed endian (i.e. the first 16 bits are swapped independently of the second 16 bits, resulting in ABCD or BADC endian, but not DCBA). Yes, that adds extra trickyness, especially if base-insn-bitsize is 32 and not 16.